In a non-volatile memory circuit (e.g., an electrically erasable programmable read-only memory (EEPROM) circuit), a control circuit produces a programming signal that typically includes two successive high-voltage pulses. These are for first causing an erasure operation and then a writing operation.
Such a programming signal PROGBIT-HV is illustrated in FIG. 1. The signal PROGBIT-HV has a calibrated total duration T0 and is provided by a high-voltage generation circuit activated by a programming command logic circuit PROGBIT. In the example, the programming signal PROGBIT is at logic 1 during the erasure/programming phase. By way of example, the typical value of the duration T0 may be 5 milliseconds with a tolerance window of 1 to 10 milliseconds.
The programming signal PROGBIT-HV has a high-voltage value HV and generally has to comply with well-specified constraints. These constraints on the characteristics (e.g., duration, high-voltage value) of the programmed signal are determined to ensure reliable programming. The duration of the programming signal should also enable sufficient charging of the memory cells. As for the maximum duration of the programming signal, it usually results from the functional specifications of the memory.
In practice, the characteristics of the programming signal vary from one integrated circuit to another due to the dispersion intrinsic to the technological manufacturing method implemented. The integrated circuits are typically tested when they come off the production line. These tests make it possible to discard those circuits whose characteristics do not come within the permissible range of values (according to the specifications of the integrated circuits).